According to the photon theory of light,which of the following physical quantities associated with a photon does not change as it collides with an electron in a vacuum?

Solar energy is incident normally on the earth's surface at the rate of about $1.4 \, kW m^{-2}$. The distance between the earth and the sun is $1.5 \times 10^{11} \, m$. Energy $E$ and mass $m$ are related by Einstein's equation $E = mc^2$,where $c = 3 \times 10^8 \, m s^{-1}$ is the speed of light in free space. The decrease in the mass of the sun is ........... $\, kg s^{-1}$.

When light of wavelength $\lambda$ is incident on a photosensitive surface,photons of power $P$ are emitted. The number of photons $n$ emitted in time $t$ is: [$h$ = Planck's constant,$c$ = velocity of light in vacuum]

$A$ $100\,W$ light source is emitting radiation of wavelength $5000\,\mathring{A}$. The rate of emission of photons is of the order of:

The radiant energy from the Sun incident on the Earth's surface is $2 \ cal/cm^2 \cdot min$. If the average wavelength of solar radiation is $5500 \ \mathring A$,then the number of photons incident per minute on a surface area of $1 \ cm^2$ on the Earth's surface is ............ $(h = 6.6 \times 10^{-34} \ J \cdot s, 1 \ cal = 4.2 \ J)$

$10^{20}$ photons of wavelength $660 \ nm$ are emitted per second from a lamp. The wattage of the lamp is (Planck's constant $h = 6.6 \times 10^{-34} \ J \cdot s$). (in $W$)